COM Full Form Hindi|What is Component Object Modell (COM)?

Definition:Component Object Model
Category:Technology » Communication

कॉम्पोनेन्ट ऑब्जेक्ट मॉडल (COM)

TAT Full Form Hindi| How the TAT works.

The Microsoft Component Object Model (COM) is a platform-independent, distributed, object-oriented system for creating binary software components that can interact. Microsoft’s OLE (compound document), ActiveX (Internet enabled components), and other technologies are built on COM.

It is important to understand that COM is not an object-oriented language, but a standard in order to fully understand it. COM does not specify how an application should look. Language, structure and implementation details can be left up to the developer. 

Instead, COM defines an object model and programming requirements to allow COM objects (sometimes called COM components or objects), to interact with other objects. These objects can exist in one process or another and even on remote computers. 

They can be written using different languages and may have structurally dissimilar structures. COM is also known as a Binary Standard. This is an acronym that refers to a standard that is applied after a program is translated into binary machine code.

Only one language requirement is for COM: code must be generated in a language capable of creating structures of pointers, and can either explicitly or implicitly call functions through pointers. C++ and Smalltalk are object-oriented languages that make it easier to implement COM objects.

However, languages like C, Java and VBScript allow you to create and manage COM objects.

COM is the defining element of a COM object. A software object is a combination of data and functions that manipulate it. A COM object allows access to an object’s information only through one or more related functions. 

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These function sets are known as interfaces and the methods of an interface are called method. Further, COM stipulates that a pointer to an interface is the only way to access the methods of an interface.

COM is responsible for defining the binary object standard. It also defines basic interfaces that provide common functions to all COM-based technology. 

COM defines how objects interact in a distributed environment. It also includes security features that help ensure component and system integrity.

This section will discuss basic COM issues that relate to designing COM objects.

The Component Object Model, (COM), is an object-based architecture that allows applications built from binary components. COM is the foundation of many Microsoft technologies, including OLE and ActiveX, Distributed COM, COM+, COM+, and Microsoft Transaction Server.Component Object Model (COM)

COM is not a programming language; it is a specification. Components are what COM allows to build applications. These COM components can be created by different vendors, at different times, and using different programming languages. Additionally, COM components are compatible with different operating systems and machines.

The Component Object Model defines a number of fundamental concepts that form the basis for the model’s structure. These are:

COM provides a standard method to create virtual function tables (vtables), in memory, for any platform (hardware or operating system combination). It also defines a standard method to call functions from the vtables. Any language that calls functions via pointers, such as C, C++ and Smalltalk, Ada or BASIC, can be used to create components that are compatible with other components made to the same binary standard. Indirection allows multiple instances of an object class to share vtables by holding a pointer. Vtable sharing is a great way to reduce memory requirements in a system that has hundreds of objects instances. Additional vtables pointing at the same component instance use less memory than multiple instances.Virtual function tables (VTBL)

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The term object can mean many things to different people. Let me clarify: An object in COM is a piece or code that provides a service to the rest. It is best to refer to an object in COM as either a component or a component to avoid confusion. This avoids confusion between COM components and source-code OOP objects, such as those in C++. COM components can support an interface called IUnknown, which will be described later. There are also a variety of interfaces depending on the functionality that the component exposes.

Although COM components often have associated data, unlike C++ objects, they will not have direct access to all COM components. Interface pointers are the only way COM components can access other components. This is a key architectural feature of the Component Object Model. It allows COM to preserve encapsulation and processing, a requirement of a true component-software standard. Transparent remoting, also known as cross-process or network calling, is possible because all data access can be made through proxy-stub pairs that forward requests from client components to server components and then send back the responses.

Through a series of functions, COM applications can interact with one another and the system.Interfaces. All OLE services can be accessed via COM interfaces. A COM interface is a highly-typed interface.ContractA small, but useful, set of semantically related operations (methods) can be shared between software components. An interface is the description of expected behavior and expected responsibilities. OLE’s drag and drop support is an example. The component’s functionality to be a drop target must be included in the collection.IDropTargetinterface; all drag source functionality is inIDragSourceInterface

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Conventionally, interface names start with “I”. OLE offers a variety of general-purpose interfaces that are useful and generally start with “I”IOle“). However, since anyone can define custom interfaces, developers can create their own interfaces while deploying component-based applications. A pointer from a COM components is actually a pointer towards one of the interfaces it implements. This means that you cannot use a COM pointer to call a method.NotAs described above, you can modify data. Here’s an example interface.ILookupTwo member methods are available:

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